The hydroforming process has application in various manufacturing and industrial processes for manufacturing parts used, for example, in automotive manufacturing, in the aerospace industry, and furniture manufacturing and in other instances where a tubular product formed to very precise dimensions and usually possessing properties of strength and lightness is desired.
A conventional hydroforming press apparatus is taught by Bowman et al. in U.S. Pat. No. 5,233,854. However, such a press apparatus is deficient in that burrs on the edges of the starting material tube can damage the O-rings used for sealing, causing the seal unit to leak. Secondly, the portion of the starting tube material extending from the ends of the dies does not usually form part of the finished product, and accordingly must be trimmed away as scrap material. As a result, the cost of manufacturing increases both in terms of the additional materials cost and the time and equipment required to trim away the excess material.
U.S. Pat. No. 5,235,836 to Klages et al. teaches a seal head for tube expansion having elastomeric rings which are protected against damage from burrs. However, as in the Bowman patent, the sealable portion of the tube extending adjacent the seal head may not match the desired shape of the final hydroformed product and must generally be trimmed away as scrap. Furthermore, the elastomeric rings periodically need to be replaced, thereby increasing manufacturing costs.
U.S. Pat. No. 4,761,982 to Snyder teaches a method and apparatus for forming a tube which eliminates the need for elastomeric rings. In the Snyder patent, a widely flaring bell section is formed in each end of the tube that generally must be trimmed away as scrap.
U.S. Pat. No. 5,475,911 to Wells et al. also describes a hydroforming tool which eliminates the need for elastomeric rings and provides wide outward flares on the workpiece outer wall. However, unless it is desired for the outer wall of the ends of the workpiece to be flared outwards, the ends of the workpiece must still be trimmed away as scrap.
Accordingly, there remains a need for a sealing apparatus which can be applied to an end of a workpiece without the need for using elastomeric rings, and that is adapted to be tailored to match a desired shape of the end portion of the product, and that can seal the net shape or desired shape of the final product, thereby eliminating or minimizing the amount of scrap material which must be trimmed away from the ends of the workpiece for a wide range of end shapes.